Process for making a bulky,multifilament,substantially twistless synthetic yarn and product thereof



Dec. 2, 1969 B. L. DAVIES ET AL 3,481,558

PROCESS FOR MAKING A BULKY, MULTIFILAMENT, SUBSTANTIALLY' TWISTLESS SYNTHETIC YARN AND PRODUCT THEREOF Filed Dec. 30, 1964 Inventor Bfifi Ez/ww vAv/e': 44AM sszwooa A Home y United States Patent US. Cl. 242159 12 Claims ABSTRACT OF THE DISCLOSURE A bulked twist-free coherent yarn consisting of polyamide filaments having a set crimp and being intermingled is obtained by subjecting the as-spun filaments, whilst still plastic to the action of a high velocity fluid jet to attenuate and molecularly orient the filaments as well as imparting a random irregular crimp thereto and causing the filaments to intermingle. A proportion of the filaments may be of the conjugate filaments composed of at least two dissimilar components.

This invention relates to synthetic filament yarns, particularly to yarns produced from high molecular weight synthetic polymers, and to processes for their preparation.

Bulky continuous multifilament yarns of high molecular weight synthetic polymers such as polyamides, characterised in that the individual filaments have coils, loops or whorls at random intervals along their length, are well known to the art. In such yarns the coils and loops are held in place by the twist usually imparted to the yarn. A convenient process for producing this yarn involves subjecting a drawn multifilament yarn to the action of a turbulent compressible fluid.

We have now discovered a useful bulky multifilament polyamide yarn in which substantially all of the filaments are characterised in that they have a random irregular crimp, which crimp persists in the individual filaments when they are pulled out from the yarn, and are intermingled to provide a twist free coherent structure.

Accordingly, therefore, from one aspect, the present invention provides a bulky multifilament yarn comprising oriented polyamide filaments having a random irregular crimp along their length, which crimp persists in the individual filaments when they are pulled out from the yarn, the filaments in the yarn being intermingled to provide a twist free coherent structure.

By intermingled is meant that substantially all of the individual filaments in the yarn are axially displaced relatively to each other so that the paths of two or more filaments cross and recross each other at random intervals along the length of the yarn.

According to another aspect the present invention provides a process for the manufacture of a bulky coherent yarn wherein molten polymers consisting of at least a major proportion of a polyamide are extruded into filaments which, whilst they are in a substantially amorphous plastic state, are subjected to the action of a fluid jet at a high velocity to provide drawing tension in the filaments above the point of application of the said fluid jet to attenuate, and molecularly orient them and at an angle to the filament path to impart random irregular crimp thereto and cause the filaments to intermingle to form a coherent yarn ice structure, the said yarn being forwarded to a yarn winding device and formed into a package and at least the polyamide filaments therein caused to crystallise.

Crystallisation of the' filaments in the yarn may be induced before the yarn reaches the wind up device, e.g. by treatment with steam before the winding device, or the filaments may be allowed to crystallise after being formed into a package either under ambient conditions or the rate of crystallisation may be accelerated by subjecting the package to a steam or heat treatment for example.

While the polyamide filaments are in the substantially amorphous plastic condition referred to above they lack, although oriented, elastic recovery and hence retain the shape into which they are formed. On subsequent crystallisation this shape is permanently set into the filaments. Thus in the process of this invention, the filaments are crimped and formed into an intermingled coherent structure by the action of the fluid jet whilst in this plastic state, subsequent crystallisation of the filaments then sets the filaments in this form.

In the normal production of polyamide yarns, e.g. form polyhexamethylene adipamide, the filaments are normally caused to crystallise immediately after extrusion, and before being substantially oriented, by passing them through what is known as a steam conditioner tube. If such a device is used in the present process in an analgous manner, e.g. by placing the tube above the fluid jet, then a nonc-oherent yarn of uncrimped filaments is obtained.

Although it is preferable that the yarn should consist solely of polyamide filaments, the presence of a minor proportion of other filaments of polymers such as polyesters, e.g. polyethylene terephthalate is permissible.

A particularly useful yarn is obtained when at least a proportion of the filaments are heterofilaments which are crimpable of subjection to some form of heat relaxing treatment. The resultant yarn has a high bulk and contains filaments having a uniform helical crimp superimposed on the random irregular crimp formed in the same filaments by the process of this invention.

By heterofilament is meant a filament consisting of two or more different components existing contiguously in either a side-by-side of sheath-core relationship along the length of the filament, such that a cross-section of the filament taken at any point along its length would reveal the components of the filament in one of the aforesaid relationships.

The crimp in the heterofilaments may be developed by relaxing before the yarn is formed into a package, e.g. by

a steam treatment which will also cause filaments to crystallise, or it may be developed after the yarn has been formed into a fabric.

Preferably the heterofilaments should consist wholly of polyamide components, e.g. 6 and 6.6 nylons, 6.6. nylon and an /206.6./ 6 nylon copolymer or 6.6. and 11 nylon, but a compatible non-polyamide component, such as a polyester e.g. polyethylene terephthalate, may be employed as a minor component.

The said fluid jet is directed such that it has a component of motion in the direction of movement of the filaments, and is arranged to act on the filaments from all sides. Thus the fluid jet is introduced to the filaments in the form of an inverted cone i.e. an annular stream down the centre of which pass the filaments. Suitably this action may be achieved using an aspirating jet one form of which will be described hereinafter.

It is thought that the angle of incidence of the fluid jet and the filaments must be sufliciently large to cause the fluid flow around the filaments to be turbulent. This turbulence may be due to the formation, within the jet, of toroidal fluid vortices which have their axes perpendicular to the mean filament axes and which break up to give a random turbulent fluid flow. Whatever the reason for the turbulent flow its effect is to cause the filaments to be whipped about and their paths to be made to cross and recross each other at random intervals and thus yield an interlaced and coherent yarn.

If the angle of incidence is too small streamline flow will result which, whilst drawing the filaments, may not provide the necessary turbulence for interlacing; if the angle is too great then an excessive amount of turbulence may result and the forwarding velocity of the fluid may not be great enough to attenuate and thus orient the filaments.

The velocity of the fluid jet required to attenuate and orient the filaments to the desired amount, which velocity is a function of the air consumption (i.e. air pressure) and aspirating jet design, will vary depending upon the polymer being spun and the process conditions including the emergent viscosity of the polymer, i.e., the melt viscosity, at the time of extrusion, the spun denier, the filament/fluid contact distance which provides the drag on the filaments, and the angle of incidence between the fluid jet and the filaments.

In general the velocity of the fluid jet must be sufficiently high to provide a resultant tension in the filaments, above the point of action of the jet on the fila ments, which will attenuate and orient the said filaments to the required extent.

The resultant tension is the algebraic sum of the tension applied to the filaments by the fluid jet acting to attenuate the filaments, and the tension caused by the melt viscosity of the polymer, surface tension effects and air drag above the point of action of the fluid jet, which act to resist attenuation of the filaments.

Since the rate of production of yarn by this process is high, in the order of 15,000 feet per minute, normal methods of winding onto yarn packages can be used only with great difliculty and the use of centrifugal and other wind-up systems are preferred. There is the added difficulty that during the crystallisation process the filaments spontaneously elongate, and if this is allowed to occur on the yarn package it will result in sloughing if normal yarn packages are wound.

The invention will now be fully explained by reference to the accompanying drawings.

In the drawings:

FIGURE I is a schematic representation of an apparatus assembly useful for forming the yarns of this invention.

FIGURE II is a cross-section of an aspirating jet suitable for use with the assembly of FIGURE I.

Referring to FIGURE I freshly formed filaments 1 are spun through spinneret 2 and are converged into a bundle at the throat of the aspirating jet 3. Within and downstream of the aspirating jet the filaments are acted upon by high velocity air which is supplied through the inlet 4. Toroidal vortices, having their axes substantially perpendicular to the mean axes of the filaments, are thought to be formed within the jet and to create a turbulent zone around the filaments causing them to be whipped from side to side and to intermingle with each other. The intermingled yarn obtained is forwarded by the blast of air is suing from the jet to the centrifugal wind up system 5.

In FIGURE II, the aspirating jet comprises a hollow body portion which is externally threaded at either end and has an air inlet pipe 11 attached thereto. A cover 12 4 and is denoted by FIGURE II. The annular air injector passageway is arranged to direct the air downwards, i.e. in the direction of filament flow.

In operation the aspirating jet may conveniently be placed at some point above the solidification point of the freshly spun filaments. The semi-solid filaments are converged together at the throat of the aspirating jet through which they are passed. In the aspirating jet the filaments are contacted by a jet of high velocity fluid which quenches the filaments, causing them to crimp in an irregular random manner. The turbulence resulting from the fluid vortices formed within the jet then cause the filaments to intermingle, and form a coherent yarn. As the yarn issued from the mouth of the jet, the high velocity fluid issuing with it forwards the yarn at substantially greater speed than the extrusion speed i.e. it exerts a drag effect on the yarn, thus causing the filaments in the yarn to be attenuated and oriented. The attenuation and orientation does not, however, take place within the jet but at some point between the spinneret and the throat of the jet, i.e. the semi-molten filaments are attenuated. The drag effect of the fluid on the yarn continues for some distance below the mouth of the jet, and it is therefore important that the wind up system for the yarn is placed below the point at which the drag becomes insignificant in order to achieve maximum attenuating efficiency. Owing to the high speeds of production of the yarn, in the order of 15,000 ft./min., the usual wind up techniques are not available and the yarn has to be packaged by a high speed wind up system. Thus, for example, a centrifugal device such as a modified Topham box, or a device such as that described in British Patent 930,546, may be used to wind up the yarn into a package.

Acceleration of crystallisation of the yarn in the package may conveniently be achieved by dropping water into the aspirating gun, the effect of the high velocity fluid atomises the water so distributing uniformly throughout the yarn and allowing more rapid and uniform crystallisation of the yarn in the package than would take place if the yarn in the package were merely allowed to crystallise under ambient conditions.

Air is the preferred fluid for the production of yarns of this invention although other gaseous fluids, may be employed. The temperature of the air may beneficially be raised above ambient temperature, care being taken however, to ensure that its temperature is low enough to have a quenching action on the yarn at its point of contact with the yarn. Increasing the temperature of the air will, of course, accelerate the crystallisation of the yarn, and if the yarn consists of or contains heterofilaments having a potential crimp, at least part of this crimp may also be developed.

The following examples illustrate convenient process for obtaining the yarn of the invention.

EXAMPLES 1 AND 2 In these examples the polymer used was polyhexamethylene adipamide having a relative viscosity of 32.6 and a melt viscosity of 475 poises at 290 C. (the spinning temperature). The polymer was spun through a 34 hole spinneret and the filaments converged into a bundle at the throat of an aspirating jet of type described with reference to FIGURE II and located at a fixed distance below the spinneret and having the following dimensions.

Inlet bore: internal diameter Vs", length 2" Exhaust bore: internal diameter length 6" Injector half angle 10 Air at ambient temperature was used as the fluid. The velocity of the air, measured in terms of air consump tion, was fixed at the required level by adjusting the size of the air injector passage, i.e. the distance apart of the inlet and exhaust bores. The coherent yarns of intermingled filaments which was obtained was collected in the amorphorus state by a device located 4 it. below the aspirating jet and allowed to crystallise under ambient conditions. The crystalline yarn had a similar appearance to that shown. Other experimental details and yarn properties are given in Table I below.

What we claim is:

1. A process for the manufacture of a bulky, multifilament, substantially twistless yarn comprising extruding molten polymers consisting of at least a major proportion of a polyamide into filaments, impinging fluid from a high velocity fluid jet upon said filaments, whilst they are in a substantially amorphous, plastic condition, to provide sufiicient tension in the filaments above the point of application of said fluid jet to attenuate and molecularly orient them, said fluid being impinged upon said filaments at an angle to the filament path to impart a random irregular crimp thereto and to cause said filaments to intermingle to form a coherent yarn structure, forwarding said yarn to a yarn winding device and forming it into a package, and causing at least the polyamide containing filaments to crystallise.

2. A process according to claim 1 wherein the molten polymers are wholly polyamides.

3. A process according to claim 2 wherein the molten polyamides consist of polyhexamethylene adipamide only.

4. A process according to claim 1 wherein at least some of the molten polymers are extruded as heterofilaments.

5. A process according to claim 4 wherein the molten polymers consist solely of polyamides.

6. A process according to claim 5 wherein the molten polymers consist of at least two polyamides selected from the group consisting of, polyhexamethylene adipamide, polyepsiloncaprolactam, polyaminoundecanoic acid and an /20 polyhexamethylene adipamide/polyepsiloncaprolactam copolymer.

7. A process according to claim 4 wherein a minor component of the heterofilaments is a polyester.

8. A process according to claim 7 wherein the polyester is polyethylene terephthalate.

9. A process according to claim 1 wherein at least the polyamide filaments are caused to crystallise before the yarn reaches the winding device.

10. A process according to claim 9 wherein the yarn is subjected to a steam treatment to cause the polyamide filaments to crystallise.

11. A process according to claim 4 wherein the yarn is subjected to a heat treatment to develop any potential crimp therein and to cause the polyamide containing filaments to crystallise.

12. The product produced by the process of claim 1.

References Cited UNITED STATES PATENTS 3,083,523 4/1963 Dahlstrom et al. l6l172 ROBERT F. BURNETT, Primary Examiner L. M. CARLIN, Assistant Examiner US. Cl. X.R. 2876; 161-173 

